SiC-Al2O_3-SiO_2复合陶瓷涂层组织结构及抗烧蚀性能研究

Microstructures and Anti-ablation Properties of SiC-Al_2O_3-SiO_2 Composite Ceramic Coatings

目的提高C/C复合材料的抗氧化性能。方法采用大气等离子喷涂在C/C复合材料表面制备SiC-Al_2O_3-SiO_2(SAS)复合陶瓷涂层,并选用氧-乙炔在1500℃对涂层进行抗氧化烧蚀性能考核。利用XRD、SEM、EDS等检测分析手段,对团聚粉末和球化粉体以及烧蚀前后涂层的成分及组织进行检测。结果经过等离子球化处理后,三种粉体流动性为90 s/50 g左右,粉末松装密度为1 g/cm^3左右。与团聚的SiC-Al_2O_3-SiO_2粉体相比,粉末流动性提升了20%左右,松装密度提高了20%,更加适宜等离子喷涂工艺。采用球化处理SiC-Al_2O_3-SiO_2粉体制备得到的涂层组织明显优于采用团聚粉体制备的涂层,涂层致密区域明显增大,内部缺陷数量和尺寸减少。在1500℃烧蚀600s后,SiC-36%Al_2O_3-4%SiO_2涂层具有最佳的抗烧蚀效果,涂层整体完整,质量烧蚀率为1.62×10^(-4) g/s。结论 SiC-Al_2O_3-SiO_2体系解决了等离子喷涂制备SiC涂层过程中沉积率低、SiC分解的问题。SiC-Al_2O_3_-SiO_2涂层具有良好的抗氧化烧蚀效果,烧蚀过程中SiO_2和Al_2O_3形成的莫来石相具有良好的高温稳定性、抗热震性以及较低的热膨胀率和氧扩散率,可以进一步提高涂层的抗氧化烧蚀效果。

The work aims to improve the oxidation resistance of C/C composites. SiC-Al2O3-SiO2(SAS) composite coatings were prepared on the surface of C/C composites by atmospheric plasma spraying, and oxyacetylene test was proceeded at 1500℃ to evaluate the anti-ablation performance. XRD, SEM, EDX and other detection methods were used to detect the agglomerated powders, plasma spheroidized powders and the composition and structure of the coating before and after ablation. After plasma spheroidization, the fluidity of three powders was about 90 s/50 g. Compared with the agglomerated SiC-Al2O3-SiO2 powder, the powder fluidity was improved by about 20%, and the normal density was increased by 20%, which was more suitable for the APS process. The microstructure and compactness of the coating prepared by plasma spheroidized SiC-Al2O3-SiO2 powder were obviously better than those prepared by agglomerated powder. After ablation for 600 s at 1500 ℃, SiC-36%Al2O3-4%SiO2 coating had the best anti-ablative effect in the group. The coating was intact and the mass ablation rate was1.62×10^-4 g/s. The SiC-Al2O3-SiO2 system solves the problem of low deposition rate and decomposition of SiC when preparing SiC coating by plasma spraying. SiC-Al2O3-SiO2 coating has good anti-oxidation ablation effect. SiO2 and Al2O3 form mullite phase during ablation, which has good high temperature stability, thermal shock resistance, low thermal expansion rate and oxygen diffusion, which can further improve the anti-oxidation ablation effect of the coating.